Thank you Peter, you are right. I have got complete information from USA Atmel's office. Maybe it will be usefull for someone:

1. AT89S8252 : Back side Markings
PDIP: e.g
Line 1 L--->R 0A1875- 19552S
Line 2 L--->R 1KOREA-H 0A0012

The mask # 19552,Rev-S,0012=is date code for testing in production.

2. For PLCC e.g 0A1875S
AT19552
1KOREA
0A0012 H
Again you see line-1,this is Rev-S again.

3.For TQFP e.g 0A1875
19552S
1KOREA
0A0012 H
Here we have line-2,which has Rev-S again.